Vessel and method for forming same

ABSTRACT

A vessel includes an inner layer forming a substantial enclosure and including a chemically inert material. An intermediate or bondable layer is mechanically attached to the inner layer. The intermediate layer can include a fibrous material. An outer layer is bonded to the intermediate layer, and surrounds at least a portion of the inner layer. A method for forming the vessel includes disposing a bondable layer against an inner surface of a mold shaped to form a substantial enclosure. A preform formed of a plastic material is disposed into the mold. The preform is heated and pressurized causing the preform to expand to conform to the mold to form the substantial enclosure, and causing the plastic material to embed into an exposed portion of the bondable layer. The substantial enclosure with the bondable layer is removed from the mold. Another item is bonded to the bondable layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a vessel, such as areinforced plastic vessel, and a method of forming the vessel.

2. Related Art

Rotomolded storage tanks are used in various industries, such aschemical, industrial, aerospace, marine, and oil and gas industries.Plastic materials are often used to manufacture such tanks, particularlyin aeronautical and deep-sea applications. The plastic material allowsfor the production of tanks that are watertight, lightweight, and ofrelatively low cost. It is often necessary, however, to reinforce thesetanks so that they are strong enough to withstand structural loads dueto the weight of the contents, operating pressures and temperatures,environmental conditions, etc.

Applying reinforcement material to these tanks can be problematicbecause most thermoplastics, and especially polyolefins, have very lowsurface energies that make it difficult or impossible to create astructural bond between the vessel wall and the reinforcing material.

SUMMARY OF THE INVENTION

It has been recognized that it would be advantageous to develop avessel, or a reinforced vessel, that is lightweight, yet able towithstand structural loads due to the weight of the contents, operatingpressures and temperatures, and/or environmental conditions, etc. Inaddition, it has been recognized that it would be advantageous todevelop a reinforced plastic vessel. Furthermore, it has been recognizedthat it would be advantageous to develop a chemically inert vesselreinforced with a fiber and resin composite material.

The invention provides a vessel device with an intermediate or bondablelayer mechanically attached to an inner layer forming a substantialenclosure. The intermediate or bondable layer can include a fibrousmaterial, while the inner layer can include a chemically inert material.An outer layer is bonded to the intermediate layer, and surrounds atleast a portion of the inner layer. The outer layer can be areinforcement layer, and can include fiber in a resin matrix.

In accordance with a more detailed aspect of the present invention, thefibrous material of the intermediate layer can be at least partiallyimbedded in the inner layer. The intermediate layer can be at leastpartially bonded to the outer layer.

In addition, the invention provides a method for forming the vessel thatincludes disposing a bondable layer against an inner surface of a moldshaped to form a substantial enclosure. A preform formed of a plasticmaterial is disposed into the mold. The preform is heated andpressurized causing the preform to expand to conform to the mold to formthe substantial enclosure, and causing the plastic material to embedinto an exposed portion of the bondable layer. The substantial enclosurewith the bondable layer is removed from the mold. Another item is bondedto the bondable layer.

Additional features and advantages of the invention will be apparentfrom the detailed description which follows, taken in conjunction withthe accompanying drawings, which together illustrate, by way of example,features of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a perspective view of a vessel in accordance with anembodiment of the present invention;

FIG. 1 b is a detailed cross-sectional view of the vessel of FIG. 1 a;

FIG. 1 c is a perspective view of another vessel in accordance with anembodiment of the present invention;

FIGS. 2 a-5 c are various schematic views of a method for forming avessel in accordance with an embodiment of the present invention;

FIG. 2 a is a perspective view of a mold shown in an open configuration;

FIG. 2 b is a partial, cross-sectional side view of the mold of FIG. 2a;

FIG. 3 a is a perspective view of the mold with a bondable layer on aninner surface thereof and a plastic material being introduced therein;

FIG. 3 b is a partial, cross-sectional side view of the mold with abondable layer therein of FIG. 3 a;

FIG. 3 ca is a perspective view of the mold with a bondable layer on aninner surface thereof and a preform formed of a plastic material beingintroduced therein;

FIG. 4 a is a perspective view of the mold shown in a closedconfiguration and being subjected to heat and internal pressure;

FIG. 4 b is a partial, cross-sectional side view of the mold with thebondable layer and a plastic material or inner layer conformed to themold and embedded into the bondable layer;

FIG. 5 a is a perspective view of a substantial enclosure with thebondable layer with a reinforcement layer being formed thereon;

FIG. 5 b is a partial, cross-sectional side view of the substantialenclosure with the bondable layer of FIG. 5 a;

FIG. 5 c is an enlarged, partial, cross-sectional side view of thesubstantial enclosure with the bondable layer of FIG. 5 b;

FIG. 6 a is a perspective view of a vacuum mold;

FIG. 6 b is a perspective view of the mold of FIG. 6 a with a bondablelayer on an inner surface thereof;

FIG. 6 c is a perspective view of the mold of FIG. 6 b with a plasticmaterial being introduced therein; and

FIG. 6 d is a perspective view of the mold of FIG. 6 c being subjectedto heat and internal pressure.

DETAILED DESCRIPTION

Reference will now be made to the exemplary embodiments illustrated inthe drawings, and specific language will be used herein to describe thesame. It will nevertheless be understood that no limitation of the scopeof the invention is thereby intended. Alterations and furthermodifications of the inventive features illustrated herein, andadditional applications of the principles of the inventions asillustrated herein, which would occur to one skilled in the relevant artand having possession of this disclosure, are to be considered withinthe scope of the invention.

As illustrated in FIGS. 1 a and 1 b, a vessel, indicated at 10, inaccordance with the present invention is shown. The vessel 10 can formor include a substantial enclosure 14, such as a tank, container, etc.Such vessels can be utilized in chemical, industrial, aerospace, marine,and oil and gas industries, and can be used to hold or contain variousdifferent materials and liquids, including for example, water, oil,gasoline, or other chemicals. The vessel 10 can include a chemicallyinert material, such as a thermoplastic, or polyolefin. Thus, the vesselcan be watertight, lightweight, and of relatively low cost. In addition,the vessel 10 can be reinforced, or can be a reinforced vessel, so thatthe vessel can be strong enough to withstand structural loads due to theweight of the contents, operating pressures and temperatures,environmental conditions, etc. The vessel 10 can be reinforced by areinforcement layer 18, such as a fiber and resin composite material.

As described above, applying a reinforcement material to a vessel can beproblematic because a chemically inert material of the vessel can have avery low surface energy that makes it difficult or impossible to createa structural bond between the vessel and the reinforcing material. Thus,the reinforcement can fail to sufficiently attach, or can laterdelaminate. Therefore, the vessel 10 or substantial enclosure 14advantageously includes a bondable layer or intermediate layer 22disposed between the substantial enclosure 14 and the reinforcementlayer 18. The bondable or intermediate layer 22 can be mechanicallycoupled to the substantial enclosure 14 and bonded to the reinforcementlayer 18. Therefore, the bondable or intermediate layer 22 couples thereinforcement layer 18 to the substantial enclosure 14.

Although the vessel 10 and the substantial enclosure 14 are shown in theFigures as having a cylindrical shape, it will be appreciated that thevessel and substantial enclosure can have any desired shape, or anon-cylindrical shape. For example, the vessel 10 and the substantialenclosure 14 can be square, rectangular, circular, spherical,pie-shaped, etc. As another example, a vessel 10 c can have a conformalshape, or a shape that conforms to, keys into, or matches another shapeor structure, such as conforming to an allocated space in an airframe offuselage of an aircraft. The term “substantial enclosure” is used hereinto describe an enclosure shaped to hold or contain a material, such asliquid, and can be shaped as a bowl, tank, container, etc. Thesubstantial enclosure 14 can include an opening 24 therein, and can besealable, such as with a lid or cap. Thus, the substantial enclosure canbe watertight. The material for the substantial enclosure can includeplastic, thermoplastic, polyolefin, polyethylene, polypropylene,polyurethane, etc. The substantial enclosure 14 can form an inner layerof the vessel 10.

The bondable layer 22 can include a fibrous material with a plurality offibers 26. Examples of the fibrous material include a fiber fabric,cloth, weave or mat. The fibers 26 can be configured in variousdifferent orientations. For example, the fibers 26 can be provided in aweave with fibers disposed in transverse orientations, weaving back andforth and overlapping other fibers. As another example, the fibers 26can be provided in chopped strands. In addition, the bondable layer 22or fibrous material can have a thickness formed by numerous overlappingfibers. The bondable layer 22 can have an inner side 30 and an outerside 34. The fibers 26 can extend between the inner and outer sides 30and 34. The bondable layer 22 or fiber 26 can include graphite,fiberglass, etc.

The reinforcement layer 18 can include a fiber in a resin matrix,indicated together at 38. The fiber of the reinforcement layer 18 caninclude continuous fibers wrapped around the substantial enclosure 14.The fiber can be graphite, fiberglass, etc.

As illustrated in FIGS. 2 a-5 c, a method for forming a vessel inaccordance with the present invention is shown. Referring to FIGS. 2 aand 2 b, a mold 100 with an inner surface 104 is shown for forming thesubstantial enclosure 14. A cavity 106 can be formed in the mold 104that is shaped to form the enclosure 14. The mold 100 and the innersurface 104 can be shaped to form the substantial enclosure 14. The mold100 can be provided in sections or halves that can be combined togetherto form the mold. The halves of the mold can be compressed together andheld in place, as shown in FIG. 4 a. The halves of the mold can becompressed by a hydraulic press or the like, as is known in the art.

Referring to FIGS. 3 a and 3 b, the bondable layer 22 is disposed on theinner surface 104 of the mold 100. The outer side 34 of the bondablelayer 22 can be an attachment portion or side secured to the innersurface 104. The inner side 30 of the bondable layer 22 can be anexposed portion or side that faces into the mold. An example of a meansfor attaching or securing the bondable layer 22 to the inner surface 104includes using an adhesive. The bondable layer 22 can be disposed aroundan entire periphery or circumference of the mold 100. For example, thebondable layer can be disposed in a cylindrical sleeve or jacket.Alternatively, the bondable layer can be disposed around an entire innersurface of the mold, so that the bondable layer surrounds the entire, orsubstantially the entire, enclosure 14. For example, the bondable layercan be disposed in a cylindrical shell with a top and bottom.Alternatively, the bondable layer can be disposed in separate anddiscrete patches at desired locations.

Referring to FIG. 3 c, a preform 108 formed of a plastic material can beintroduced into the mold 100. The preform 108 can be a hollow blank ortube with a fluid or air channel extending therethrough. Alternatively,the preform can have a different shape, and can be injection molded intovarious different shapes. The mold 100 can then be closed or sealed.Referring to FIGS. 4 a and 4 b, the mold 100 with the preform 108therein can be heated, indicated at 110. The heat 110 can be applied byheating elements associated with the mold, as is known in the art. Inaddition, the preform 108 can be pressurized, such as by a pressuresource 112. The simultaneous heat 110 and pressure cause the preform 108to expand and compress against the inner surface 104 of the mold 100,and against the bondable layer 22. The plastic material adheres as afilm to the interior surface of the mold, and/or the exposed portion 30of the bondable layer 22. A plastic layer will result which forms thewall of the substantial enclosure. The plastic film or material willharden as the mold cools. The mold can be opened and the substantialenclosure removed. The molding process can form a substantial enclosurethat is seamless and hollow, and with a substantially constant wallthickness.

Heating and pressurizing the mold 100 and the plastic material of thepreform 108 causes the plastic material to conform to the mold 100, andto form the substantial enclosure 14. In addition, heating andpressurizing the plastic material 108 causes the plastic material toembed into the exposed portion 30 of the bondable layer 22 on the innersurface 104 of the mold 100. The plastic material permeates into athickness of the bondable layer, and embeds into the fibrous materialand around individual fibers or portions of individual fibers. Theplastic material can substantially surround portions of the fiber,forming a mechanical attachment. For example, individual fibers canweave back and forth, into and out of the plastic material, indicated at112 in FIG. 5 c. As another example, entire fibers of a mat or weave canbe embedded within the plastic material, indicated at 116 in FIG. 5 c.The embedded plastic attaches the bondable layer 22 to the substantialenclosure 14. Thus, the bondable layer 22 or fibrous material isintegrally molded into the substantial enclosure 14 or plastic materialthereof. Furthermore, heating and rotating causes the plastic materialto form an inner layer of the substantial enclosure 14 or vessel 10. Thebondable layer 22 forms a layer around at least a portion of the innerlayer.

While the exposed portion 30 of the bondable layer 22 is embedded intothe plastic material of the substantial enclosure 14, the attachmentportion 34 of the bondable layer becomes exposed when removed from themold. The bondable layer 22, attached to the substantial enclosure 14 orinner layer, allows other items to be secured to the substantialenclosure 14 by attaching to the bondable layer, or attachment portion34 thereof. Referring to FIG. 5 a, the other items can include areinforcement layer 18, such as a fiber in a resin matrix. Thus, thebondable layer 22 can form an intermediate layer between the other itemor reinforcement layer 18, and the substantial enclosure 14 or innerlayer. The reinforcement layer 18 can extend around a periphery orcircumference of the substantial enclosure 14. For example, fiber can becontinuously wound around the substantial enclosure 14 and the bondablelayer 22. The fiber and resin can bond to the fibrous material of thebondable layer. Thus, the reinforcement layer 18 can bond to thebondable layer 22, while the bondable layer can be mechanically attachedto the substantial enclosure 14 or inner layer. The fiber can be appliedby continuous automatic winding, manual lay-up, fiber placement,automated tape, or other manual or automatic methods, and other types orconfigurations of fiber.

Other types of thermal forming can be used to form the vessels,including for example, vacuum forming or similar processes. Referring toFIG. 6 a, a vacuum mold 200 with an inner surface 204 is shown forforming the substantial enclosure 14, or portion thereof. A cavity 206can be formed in the mold 200 that is shaped to form the enclosure 14,or a portion thereof. The mold 200 and the inner surface 204 can beshaped to form the substantial enclosure 14, or a portion thereof. Themold 200 can be provided in sections or halves of the substantialenclosure that can be combined together to form the substantialenclosure. A plurality of apertures 208 can be formed in the innersurface 204 of the mold and connected to a vacuum source 210, such as apump. The vacuum source 210 can be used to create a pressuredifferential, discussed below.

Referring to FIG. 6 b, the bondable layer 22 is disposed on the innersurface 204 of the mold 200, as described above. Referring to FIG. 6 c,a sheet 212 formed of a plastic material can be disposed on or over themold 200. The sheet 212 can be planer or flat, or can be a differentshape. Referring to FIG. 6 d, the mold 200 and/or sheet 212 can beheated. The heat can be applied by heating elements associated with themold, as is known in the art. Alternatively, separate heaters can heatthe sheet. In addition, the sheet 212 can be subject to a pressuredifferential, such as with the vacuum source 210. The heat and vacuum(ambient pressure) cause the sheet 212 to compress against the innersurface 204 of the mold 200, and against the bondable layer 22. Theplastic material adheres to the interior surface of the mold, and/or theexposed portion 30 of the bondable layer 22. A plastic layer will resultwhich forms the wall of the substantial enclosure, or a portion thereof.The sheet and/or mold can be cooled. The substantial enclosure 212 canbe removed from the mold 200. The vacuum forming process can form asubstantial enclosure, or portion of the substantial enclosure that canbe combined with others to form the substantial enclosure. Heating andapplying a vacuum to the plastic material of the sheet 212 causes theplastic material to conform to the mold 100, and to form the substantialenclosure 14, as described above. In addition, heating and applying avacuum to the plastic material causes the plastic material to embed intothe exposed portion 30 of the bondable layer 22 on the inner surface 204of the mold 200. Other items can be secured to the substantial enclosure14 by attaching to the bondable layer, or attachment portion 34 thereof,as described above.

Alternatively, the mold 200 can have a protrusion, as opposed to acavity, with the plurality of apertures therein; and the sheet 212 canbe formed against the protrusion.

Other types of molding or thermoforming can be used, including forexample, resin transfer molding (RTM), twin sheet forming, etc.

It is to be understood that the above-referenced arrangements are onlyillustrative of the application for the principles of the presentinvention. Numerous modifications and alternative arrangements can bedevised without departing from the spirit and scope of the presentinvention while the present invention has been shown in the drawings andfully described above with particularity and detail in connection withwhat is presently deemed to be the most practical and preferredembodiments(s) of the invention, it will be apparent to those ofordinary skill in the art that numerous modifications can be madewithout departing from the principles and concepts of the invention asset forth in the claims.

1. A vessel device, comprising: a) an inner layer forming a substantialenclosure and including a chemically inert material; b) an intermediatelayer, mechanically attached to the inner layer; and c) an outer layer,bonded to the intermediate layer, and surrounding at least a portion ofthe inner layer.
 2. A device in accordance with claim 1, wherein theouter layer is a reinforcement layer and includes fiber in a resinmatrix.
 3. A device in accordance with claim 1, wherein the intermediatelayer includes fibrous material at least partially imbedded in the innerlayer.
 4. A device in accordance with claim 3, wherein the outer layerincludes continuous fiber wound around a perimeter of the vessel.
 5. Adevice in accordance with claim 1, wherein the intermediate layerincludes a fabric or mat with fibrous material.
 6. A device inaccordance with claim 1, wherein the intermediate layer is at leastpartially imbedded in the inner layer and at least partially bonded tothe outer layer.
 7. A device in accordance with claim 1, wherein theintermediate layer and the outer layer extend around a perimeter of thesubstantial enclosure.
 8. A vessel device, comprising: a) an inner layerforming a substantial enclosure; b) the inner layer including achemically inert material; c) a bondable layer, coupled to the innerlayer, having an inner portion imbedded in the inner layer and an outerportion exposed and extending beyond the inner layer; and d) anotheritem, bonded to the bondable layer.
 9. A device in accordance with claim8, wherein the another item includes a reinforcement layer substantiallysurrounding the substantial enclosure, the reinforcement layer includingfiber in a resin matrix.
 10. A device in accordance with claim 8,wherein the bondable layer includes fibrous material at least partiallyimbedded in the inner layer.
 11. A device in accordance with claim 8,wherein the bondable layer includes a fabric or mat with fibrousmaterial.
 12. A device in accordance with claim 8, wherein the bondablelayer extends around a perimeter of the substantial enclosure.
 13. Avessel device, comprising: a) a substantial enclosure having an outersurface; b) the outer surface including a chemically inert material; c)a bondable layer, at least partially imbedded in the outer surface ofthe substantial enclosure; and d) another item, bonded to the bondablelayer.
 14. A device in accordance with claim 13, wherein the anotheritem includes a reinforcement layer substantially surrounding thesubstantial enclosure, the bondable layer including fiber in a resinmatrix.
 15. A device in accordance with claim 13, wherein the bondablelayer includes fibrous material at least partially imbedded in theenclosure.
 16. A device in accordance with claim 13, wherein thebondable layer includes a fabric or mat with fibrous material.
 17. Adevice in accordance with claim 13, wherein the bondable layer is atleast partially imbedded in the enclosure and at least partially bondedto the another item.
 18. A vessel device, comprising: a) a substantialenclosure having an outer surface; b) a bondable layer, at leastpartially imbedded in the outer surface of the substantial enclosure;and c) a reinforcement layer including fiber in a resin matrixchemically bonded to the bondable layer, and surrounding at least aportion of the substantial enclosure.
 19. A method for forming a vessel,comprising the steps of: a) disposing a bondable layer against an innersurface of a mold shaped to form a substantial enclosure; b) disposing aplastic material into the mold; c) heating and pressurizing the plasticmaterial causing the plastic material to conform to the mold to form thesubstantial enclosure, and causing the plastic material to embed into anexposed portion of the bondable layer; d) removing the substantialenclosure with the bondable layer from the mold; and e) bonding anotheritem to the bondable layer.
 20. A method in accordance with claim 19,wherein the step of disposing a bondable layer includes disposing abondable layer including fibrous material; and wherein the step ofcausing the plastic material to embed includes causing the plasticmaterial to embed into the fibrous material.
 21. A method in accordancewith claim 19, wherein the step of bonding another item to the bondablelayer includes bonding a fiber with a resin matrix.
 22. A method inaccordance with claim 19, wherein the step of disposing a plasticmaterial includes disposing a preform in the mold; and wherein the stepof pressurizing includes pressurizing the preform to expand.
 23. Amethod in accordance with claim 19, wherein the step of disposing aplastic material includes disposing a sheet over the mold; and whereinthe step of pressurizing includes applying a vacuum to the sheet.
 24. Amethod for forming a vessel, comprising the steps of: a) disposing abondable layer against an inner surface of a mold shaped to form asubstantial enclosure; b) introducing a plastic material into the moldand causing the plastic material to conform to the mold to form asubstantial enclosure; c) causing the plastic material to embed into anexposed portion of the bondable layer in the mold and attaching thebondable layer to the substantial enclosure; and d) removing thesubstantial enclosure with the bondable layer from the mold.
 25. Amethod in accordance with claim 24, wherein the step of disposing anattachment portion of a bondable layer includes disposing a bondablelayer including fibrous material; and wherein the step of causing theplastic material to embed includes causing the plastic material to embedinto the fibrous material.
 26. A method in accordance with claim 24,further comprising the step of: bonding another item to the bondablelayer.
 27. A method in accordance with claim 26, wherein the step ofbonding another item to the bondable layer includes bonding a fiber witha resin matrix.
 28. A method in accordance with claim 24, wherein thestep of introducing a plastic material includes disposing a preform inthe mold; and wherein the step of causing the plastic material to embedincludes pressurizing the preform to expand.
 29. A method in accordancewith claim 24, wherein the step of introducing a plastic materialincludes disposing a sheet over the mold; and wherein the step ofcausing the plastic material to embed includes applying a vacuum to thesheet.